William Binney, a mathematician who worked for the NSA for 32 years as a cryptographer, goes on the record to detail that the FBI’s going through General Petraeus’s email is no particular exception: all electronic communications of all Americans are under constant surveillance and are permanently stored so security agencies can look through them whenever an urge strikes:

Mr. Binney blew the whistle on the NSA under the George W. Bush administration. Asked what has changed under the Obama administration, Mr. Binney responds (5:30):

The change is, it’s getting worse. They’re doing more. I mean, he [Obama] is supporting the building of the Bluffdale facility, which is over $2 billion they’re spending on storage, alone, of data. So that means they’re collecting a lot more now and they need more storage for it.

Furthermore, by his calculations, presented by sworn affidavit to the court for a lawsuit against the NSA, the new facility would hold 5 zettabytes of data. For context, according to Wikipedia, the entire World Wide Web contains one-half zettabyte of information.

Information is power, and Mr. Binney explains its particular appeal now (7:30):

This government doesn’t want things in the public. It’s not a transparent government.

And for those who think, “Go ahead and collect and store all that data on me. I’m not doing anything wrong:”

The problem is, if they think they’re not doing anything wrong, they don’t define that. The central government does. The central government defines right and wrong and whether they target you. So it’s not up to the individual. ... If their position on something is against what the administration has, then they could easily become a target.

See also, this piece from the New York Times in which Mr. Binney details how the NSA has spied on “everyone in this country” since 9/11.

The video interview above is long at 12 and a half minutes, but well worth your time. If you’re not afraid of your government, you’re just not paying attention.